A recent wireless local area network (WLAN) system adopts a slotted channel access to reduce collisions between stations during an operation of a basic service set (BSS) including thousands of stations. When thousands of stations access a channel and attempt to perform transmission at the same time, a collision probability may increase. In the slotted channel access method, a restricted access window (RAW) may be set to prevent collisions, and a transmission duration in the RAW transmission duration may be divided into slots. A slot in which transmission is allowed may be allocated to each station. A station may be allowed to contend for transmission in a slot allocated to the station. Thus, a sudden surge of channel accesses may be distributed, and collisions may be reduced.
In addition, the WLAN system introduces a relay operation to extend the coverage of an access point (AP). In a case in which the relay operation is employed, the slotted method may be adopted to efficiently support transmission of a large number of stations.